Detection of Toxoplasma gondii in cured meats

Congenital toxoplasmosis is associated with acute maternal infection acquired during or shortly before the pregnancy. The mother's infection is initiated by the ingestion of one of the life forms of the parasite but the relative importance of the different sources of toxoplasmosis are not established. Recent epidemiological studies have confirmed ingestion of raw meats as a risk factor but also identified consumption of cured meats as being associated with acute toxoplasmosis in pregnancy. There is little existing information concerning the efficiency of commercial curing processes for inactivating Toxoplasma gondii. We sought to detect the presence of T. gondii in ready-to-eat cured meat samples by amplification of the parasite's P30 gene using the polymerase chain reaction (PCR). In addition, tissue culture was used in order to isolate viable parasites. Laboratory inoculated specimens were used to assess the sensitivity of each method. PCR was able to detect parasite contamination down to a level of 5 x 10(3) trophozoites/g while viable toxoplasma could be detected in tissue culture at a level of 10(3) trophozoites/g cured meat. The high salt content of some cured meats limited sensitivity of the PCR assay by inhibition of the polymerase enzyme and reduced the sensitivity of tissue culture due to osmotic pressure causing cytopathic effect. However viable T. gondii was detected in one out of 67 ready-to-eat cured meat samples. Our results highlight the need for improved methods for detecting toxoplasma contamination of food. Health implications of consuming cured meats in pregnancy require careful consideration.